Vous devez vous connecter ou créer un compte utilisateur pour candidater. Les candidatures transmises via d’autres plateformes ou sites ne seront pas prises en compte.

Intitulé du sujet: Glucocorticoid Hormone Receptors in Peripheral Nervous System Myelination

Sujet

Codirection:

Nombre de mois: 48 mois

Ecole Doctorale: ED 563 - Médicament,Toxicologie, Chimie, Imageries

Unité de recherche et équipe:

Unité Inserm UMRS1124 (T3S), HealthFex au 1er janvier 2025

Equipe 3. 'Myelination and nervous System Pathologies'

Coordonnées de l’équipe:

Unité Inserm UMRS1124

Université Paris Cité

Campus Saint Germain des Près

45 rue des Saints Pères

75006 Paris

Secteur: Sciences de la vie / Life Sciences

Langue attendue: Anglais

Niveau de langue attendu: B2

Description

Description du sujet:

Myelination ensure a fast and coordinate nerve influx as well as trophic support for axons. In the peripheral nervous system, Schwann cells (SC) produce the myelin sheaths insulating axons (Boullerne; Exp Neurol. 2016). Demyelination occurs in several pathologies including auto-immune diseases such as Guillain–Barré syndrome (Shahrizaila et al; Lancet. 2021), genetic diseases such as Charcot-Marie-Tooth often caused by mutations in myelin-associated genes (Higuchi, Takashima; J Hum Genet. 2023), and diabetic neuropathy (Naruse K; Adv Exp Med Biol. 2019). Myelination is regulated by many factors including some receptors to steroid hormones such as sex hormones (Magnaghi; Brain Res Brain Res rev; 2001). Mineralocorticoid and Glucocorticoid Receptors (MR and GR respectively) are steroid receptors that bind glucocorticoid hormones (GC), mediating their effects differentially. MR is a high affinity receptor for GC. It also can bind the mineralocorticoid hormone aldosterone in tight epithelia regulating transepithelial ionic transport, while GR is a lower affinity receptor (Le Menuet, Lombès; Steroids. 2014). To date, while their role on the central nervous system is extensively studied there is little data on the action of MR and GR in peripheral nervous system (PNS), and more particularly in myelination (Girard; J. Steroid Biochem. Mol Biol. 2010). To better delineate their specific role, we first undertook MR knockout specifically in mouse SC (SCMRKO mice) using deserthedgehog gene promoter driving CRE recombinase expression (dhhCRE construct). These animals presented a compensatory increase in GR expression associated with myelin sheath enlargement in the sciatic nerves (Gonzales-Mayoral et al; J Endocrinol. 2023). These results encouraged us to study further the role of these two glucocorticoid receptors in the PNS.

This thesis project focus on the characterization of glucocorticoid actions in SC analyzing MR and GR signaling. We generated an additional mouse model with a GR inactivation in SC (SCGRKO) as well as another harboring the double knockout of MR and GR in SC (SCdKO). The latter being currently generated by breeding the two aforementioned mouse models. Already, we found that SCGRKO animals present motor alterations in behavioral tests. Beside motor functions, SCGRKO, SCdKO animal phenotypes will be compared to their control littermates analyzing their peripheral nerves (such as sciatic nerve) by immunohistochemistry, electronic microscopy, and measuring their RNA (qPCR) and protein (Western Blot) expression in adult mice. This task is already well advanced for SCMRKO animals. In addition, transcriptomic analysis will be undertaken on adult sciatic nerves of the 3 animal models and their control littermates to better understand glucocorticoid signaling pathways in myelination. SC primary cultures, that can be derived form knockout animals and their controls, as well as SC-derived immortalized cell line will be used for mechanistic studies. Eventually, the role of MR and GR in nerve degeneration/regeneration will be investigated using nerve crush experiments in SCMRKO, SCGRKO and SCdkO mice comparing the kinetic and the extent of the recovery process, using morphological and gene/protein expression analysis.

Given the importance of glucocorticoid hormone actions on stress, circadian rhythms, immunity and metabolism whose dysregulations are involved in pathologies induced by modern lifestyle, potentially affecting the peripheral nervous system, and given the widespread prescription of glucocorticoid drugs, we believe that a better understanding of GC actions on peripheral myelination is of public health interest.

Compétences requises:

Spoken and written English required

Molecular Biology

Cell culture

Animal experimentation on rodent

Organized and reliable

Références bibliographiques:

Boullerne; Exp Neurol.2016: Sep;283(Pt B):431-45.

Girard; J.Steroid Biochem. Mol Biol. 2010 Oct;122(4):149-58.

Gonzales-Mayoral et al; J Endocrinol. 2023: Jul 12;258(2):e220334.

Higuchi,Takashima; J Hum Genet. 2023: Mar;68(3):199-214.

Le Menuet, Lombès; Steroids. 2014: Dec:91:11-9.

Magnaghi et al; Brain Res Brain Res rev; 2001

Naruse K; Adv Exp Med Biol. 2019: 1190:345-356.

Shahrizaila et al; Lancet. 2021: Mar 27;397(10280):1214-1228.